Radio receiving system



Nov; 10, 1931. ,J TRAINQR 1,831,519

RADIO RECEIVING SYSTEM- Filed Dec. 15, 1927 2 Sheets-Sheet l Y L 25 L Nov. 10, 1931. F.'J. TRAINOR I RADIO RECEIVING SYSTEM Fi'led Dec. 13, 1927 2 Sheets-Sheet 2 J0 vm/ 44 y- Q Patented Nev. 10, 1931 UNITED STATES Arum OFFICE.

FOSTER J. TRAINOR, 0F DAYTONA BEACH, FLORIDA, ASS'IGNOR, OF ONE-HALF T0 A. J. MALBY, DAYTONA BEACH, FLORIDA RADIO RECEIVING SYSTEM Application filed December 13, 1927. SerialNo. 239,713.

My invention relates to improvements in radio receiving systems, and has to do, more particularly, with such systems employing tuned radio frequency. i

The principal object of my invention is to provide a radio receiving system of this character having greatly improved selectivity and tone quality, due to the improved means employed for tuning a plurality of grid circuits to the identical resonance period. A further object of my invention is to provide such a receiving system, in which less power is required for its operation, thus resulting in more eflicient and economical operation, and in better tone quality and less-static and other disturbances because of the fact that lower plate voltages are employed. Another object of my invention is to provide such a radio receiving system, which can be constructed very economically, inasmuch as the necessaryparts of the set are less in number, simple and inexpensive. A further object of my invention is to provide a radio receiving system in which a plurality of radio fre quency circuits may be tuned'from a single dial by simple and inexpensive means, which will tune all of the radio frequency circuits simultaneously to the same resonan'ce period, throughout the range of the tuning device, and which. do away with the necessity for employing expensive matched tuning devices, or balanced condensers, introducing losses or broadened tuning to compensate for the difference in condensers.

Further objects, and objects relating to details and economies ofconstruction and operation. will definitely appear from the detailed description to follow. In one instance, I accomplish the objects of my inven? tion by the devices and means set forth in the following specification. My invention is clearly defined and pointed out in the appended claims. A system constitutingone embodiment of my invention is illustrated inthe accompanying drawmgs, forming a part of this specification, in which Figure l is a wiring diagram illustrating the radio frequency end ofa receiving set embodying my invention, comprising a deand tector andone stage of radio frequency amplification; I Fig. 2 is a wiring diagram illustrating the radio frequency end, of a receiving set embodying myinvention, comprising a detector and twostages ofradio frequency amplification; v

Fig. 3 is a view, in side elevatiomof a coil structure, which I employ as a means for. effecting substantially identical inductive coupling between a plurality of circuits, part of this coil. being broken away to show the primary windings inductively coupled there with; p r

Fig. 4 is an enlarged, fragmentary view showing the way in v which three-wires are braided together to form a braid from which the coil shownin Fig. 3 is formed;

Fig. 5 is a view, in side elevation, of an alternative form of coil structure in which three circuits, comprising two secondary windings of radio frequency transformers and a coil connected in the tuningcircuit, are so arranged with respect to each other that each has a substantially identical coupling with respect to the others, and are inductively coupled with the primaries of the radio frequency transformers;

Fig. 6 is a top plan view of the coil structure shown in Fig. 5;

Fig. 7 is a fragmentary iew showing four wires braided together in the manner employed when a coil structure is to be formed in which four circuits are inductively coupled with substantially identical coupling,

Fig. 8 is a similar view showing five wires braided together in the form employed in forming a coil structure in which five circuits. are to beinductively oupled with a substantially identical coupling.

. In the drawings, the same reference numeralsrefer to the same parts throughout the several views j In a. radio receiving system employing radio frequency, itis highly desirable thatthe several radio frequency grid circuits be. tuned to the same resonance period in orderto permit of eflicient reception of the=desired signals, and the t-one'quality and seion lectivity of the system depend upon the accuracy with which the several radio frequency grid circuits may be tuned to the identical resonance period. Heretofore, it has been the practice to provide a separate tuning device, such as a variable condenser, connected in each of the several grid circuits to be tuned. hen these several tuning devices are not connected with each other, the tuning of the radio frequency grid circuits depends upon the ability of the operator to adjust manually each of these several tuning devices, usually three, so as to tune each of the grid circuits to the identical resonance period. This is a difiicult thing to do and the later developments in this art have been along the line of providing mechanical connections between the several tuning devices, so that they may be simultaneously operated from a single dial, or, in some cases, two tuning devices are coupled together so as to be operated by a single dial so that the dial control is reduced from three to two. This mechanical coupling of several tuning devices, so that they may be operated by a single dial, is very difficult and, in fact, it has been found 'to be commercially impractical to tune several grid circuits simultaneously and accurately to the identical res onance period from the same dial. The tuning devices or variable condensers differ a great deal, and the characteristics of several tuning devices will vary at different points in the range, with the result that it has been a difficult and expensive to balance the several tuning devices, which are mechanically connected to be operated by a single dial. Furthermore, in order to prevent so far as possible any inductive effect of one radio frequency circuit upon another, it has been the practice to provide shields to cut off any inductive coupling between the several stages of radio frequency amplification, and many expensive and elaborate devices have been used to shield the several stages from any inductive efiect on each other.

My invention consists in tuning a plurality of grid circuits by' means of a single tuning device connected in a master tuning circuit, which tuning circuit is inductively coupled with each of the grid circuits to be tuned.

An inductive coupling should exist between the tuning circuit and each of the circults to be tuned, and, preferably, each of the circuits to be tuned shouldihave the same inductive eifect upon each of the other circuits. In this way, the tuning device acts to tune the master tuning circuit to a certain resonance period, and each of the grid circuits is simultaneously tuned to the identical resonance period by reason of the inductive coupling between these grid circuits and the tuning circuit. In this way, the set can be controlled from a single dial without the necessity for a plurality of tuning devices mechanically connected together, and all the difliculties incident to such mechanical connections between separate tuning devices are eliminated. There is no need for the use of balanced tuning devices and, hence, a simple variable condenser in the master tuning circuit suffices to tune the whole set, and considerable economy is efiected. The balance is built into the set, in that, when the set is built, the several grid circuits to be tuned lectivity. Furthermore, this results in a very marked economy, as a large number of parts ordinarily used may be done away with, there is no need for building matched tuning devices or condensers, the set may be made more compact and, hence, requires a smaller cabinet and adds to its portability, the same signal strength can be secured with a less number of audions as compared with the sets new in use, and much less power is required for the operation of this system.

Furthermore, my invention consists in providing a transformer structure in which a number of circuits are brought into such relation that each circuit has an identical inductive coupling with the other, by braiding the wires in said several circuits into a symmetrical braid, which braid is formed into a coil, with which the primaries of the transformer structure are inductively coupled.

This is a simple, inexpensive and convenient means for arranging several secondaries of the radio frequency transformers in such inductive and capacitive relation to each other, and to a tuning coil or circuit, that there will be an identical coupling between each of the several windings.

Referring tothe numbered parts of the drawings, in which I have illustrated a system embodying my invention, I have shown in Fig. 1 the radio'freqnency end'of a receiv ing system embodying my invention and employing a detector tube and one stage of radio frequency amplification. Referring to this figure, the primary winding 11, of the first radio frequency transformer, is connected in series between the antenna 10 and the ground 12. The grid of the audion'13 is connected by wire 14 to the secondary winding 15, which is inductively coupled with the winding 11. The winding 15 is connected by wire 16 with the movable arm 17 of a potentiometer 18, which potentiometer is connected across the filament circuit by the wires 19 and 20. The plate of the first audion 13 is connected by Wire 21 to the primary winding 22, which is inductively coupled with the secondary windin 30 of the second radio frequencytransformer, and the winding 22 is connected by wire 23 to the positive side of the B -bat- 5 tery 24. The negative side of the B-batt'ery is connected by wire 39 to the A the A battery '25, and the positive side of the i l-battery is connected to the filament circuitby wire 26. The other side of the filament circuit comprises the wire 28, the Va:- 'ri'able resistance 27, and the wire 40 connecting said resistance with the negative side of th A-battery 25. The secondary winding 30, of the second radio frequency transformer, is connected by wire 29 to the filament ci r-' cult, and by wire 31 to the grid of the detector tube 33, a grid leak 32 being introduced in the line 31 leading to the grid The plate of the detector tube is connected by wire 34 to one of the output terminals, the other output terminal bein connected by wire 3'5 to B-battcry 24 at whatever point is necessary for proper detection and rectification in the detector stage. The ear phones may be connected to the out-put terminals or, if desired, several stages of audio frequency amplification, of usual form and design, may be connected to these out-put terminals.

It will be observed that no tuning devices are located in the grid circuits including the windings 15 and 30, These circuits are simultaneously tuned to the identical resonance period by means of a. tuning circuit in cluding a tuning coil 36, and a variable condenser 37. The tuning coil 36 is inductively coupled with each of the coils 15 and 30 with an identical inductive coupling, so that the tuning circuit has the same inductive effect upon each of these secondary windings, and the secondary windings 15 and 30 are so arranged, with respect to each other, that each has a like inductive effect upon the other. In order to prevent sensitivity to body ca pacity, the tuning circuit may be grounded by aconnection, as indicated in dotted lines at 38, to the wire 16 leading to the potentiometer arm connected in the filament circuit.

'lhe impedance of the tuning circuit may be varied by adjusting the variablecondenser 37. and, thus, the tuning'circuit may be tuned to any resonance period. Since this tuning circuit is inductively coupled by an identical coupling with each of the grid circuits, these grid circuits are simultaneously tuned to the same resonance period as determined by the timing device or variable condenser. Thus, a plurality of grid'circuits are simultaneously tuned to the identical resonance period, under the control of a single tuning device, by means of a single dial, without the necessity for any mechanical connection between a series of tuning devices, without the'need for positive side of balancing such tuning devices, and without the need of providing means for shielding the several radio frequency transformers the means for tuning a plurality of grid circ'uits from a sin le tuning device. 7

Referring to ig. 2,1 have illustrated a radio receiving system embodying my invention and employing a detector tube and two stages of radio frequency amplification. In

this figure, the primary winding 11 is connected in series between the antenna and ground 12. The grid of the first radio frequency tube 13 is connected by wire 14 to the winding 15-, which is inductively coupled with the primary winding 11. Winding 15 is connected by wire 16 with the movable arm 17 of a potentiometer 18, which is connected across the A-battery by the leads 19 and 20. The plate of the first audion 13 is connected by wire 21 to the primary winding 22 of the second radio frequency transformer, said winding being connected by wire to the positive side of the B-battery 24 The negative side of the B-battery is connected by wire 39 to the positive side of the A battery 25, the positive side of said A- battery being connected by lead 26 with the filaments of the several *audi-ons, and the filament circuit being completed by lead 28 connected to said filaments and to a variable resistance 27, which is connected by wire to the negative side of the A-battery 25. The grid of the second an-(lion 33 is connected by wire 31 to the secondary. WindingBG of the second radio frequency transformer, which winding is inductively coupled with the primary winding 22, and is connected by wire with the lead 16. The plate of the second audion '3-3 is connected by the lead 41 to the primary winding 42 of the third radio frequency transformer,- which winding is con nected by wire 43 to the lead 23 leading to the positive side'ofithe B-battery. The primary windinig42 is inductively coupled with the secondary winding 44, which isoonnected by wire 45 with the grid of the detector tube 46, the grid leak 32 being introduced in the lead 45. The winding 44 is also connected by the lead 47 with the positive side of the A- batte'ry 25. The plate of the detector tube 46 is connected by "the lead 48 to one of the output terminals, the other out-put terminal being' conlfec't'ed "by wire 49-with the Bhutt'ery'24, at Whatever point is necessary for proper detection rectification in the dctector stage. The ear phones may be connected directly to the out-put terminals, or one or more-stages of audio frequency a1nplili'c-a'tionof usual and approved design may be connected to such terminals, as desired.

Flt, will be observed that there are no tuning device's included inthe 'gr' id circuits, which include the coils er windings 1'5, and 4A. In order to tune these :three grid circuits simultaneously to the identical resonance period, I provide the tuning circuit including the tuning coil 50 and the variable condenser 51. The tuning coil is inductively coupled with each of the windings 15, 30 and 4A with substantially identical inductive coupling, so that the tuning coil 50 shall have a like inductive effect upon each of the coils 15, 30 and 44 connected in the grid circuits, and these coils are preferably all so connected and related that each one of them will. have an identical inductive eifect upon each of the others. In Fig. 2, the coils which are to be coupled with an identical inductive coupling are shown as linked together by dotted lines, which are used to indicate diagrammatically such inductive coupling. The tuning circuit in cluding the coil 50 may be tuned, by means of the variable condenser 51, to any desired resonance period, and due to the like inductive coupling existing between said tuning coil 50, and each of the coils 15, 30 and 3a in the several grid circuits, each of the grid circuits will be tuned simultaneously to the identical resonance period by means of a single tuning device, without the interposition of mechanical connections between a series of tuning devices, or the use of matched variable condensers, or other expedients such as have been resorted to in the past.

In order to arrange the several grid circuits and the tuning circuit in such relation to each other that an identical inductive and capacitive coupling will exist between them, I prefer to braid together the wires constituting part of the grid and tuning circuits, in a symmetrical braid, and to form this braid into a coil. Thus, as shown in Fig. 4, the windings and 30, shown in Fig. 1, are braided with the winding 36, in the tuning circuit, in a symmetrical braid, in which each wire passes'over and around every other wire in the braid the same number of times and in the same manner. The braid thus formed is then coiled. The primary winding 11 is coiled co-aXially with the coil formed from the braid and positioned near one edge of that coil. The primary winding 22, connected in the plate circuit of the first tube, is also formed into a coil co-axial with the braid coil, and is positioned within said coil, near one end thereof, as shown in Fig.2. By means of this structure, the windings 15, 36 and are coupled to each otherwith identical inductive coupling, and each bears the same inductive and capacitive relationship to the primary windings 11 and 22.

When there are four circuits to be inductively coupled in this manner, as in the system shown in Fig. 2, for instance, the braid will be formed as shown in Fig. 7, in which four wires are braided together in a symmetrical braid. Thus,.I have illustrated, in Fig. 7, the wires comprising the windings 15, 30, 4 1 and braided together, and this braid is subsequently formed into a coil structure with which the primary windings 11, 22 and 12 are inductively coupled. Similarly, if four grid circuits and a tuning circuit, comprising five windings in all, are to be inductively coupled, in such a way as to provide for an identical inductive coupling between them, the wires will be arranged as shown at 53, 54, 55, 5.6 and 57 in Fig. 8, and the symmetrical braid thus formed is then formed into a coil structure within which the primary coils may be so arranged as to provide for the proper coupling with the braid coil.

In case there are but two grid circuits to be inductivey coupled with a tuning circuit, as in the hook-up shown in Fig. 1, this can be effected by the means shown in Figs. 5 and 6, if desired. In this case, the primary coils 11 and 22 are on the inside and the secondary windings 15, and 30 are wound around the primary windings in the usual manner. The coil 36, in the tuning-circuit, is wound around the primary coils in the same manner and located between the coils 15 and 30, co-axially therewith, so that the tuning coil 36 will have a like inductive effect upon each of the coils 15 and 30, and so that the coil 30 will have an identical inductive coupling with the coil 15, and vice versa. This is an alternative means for arranging these circuits in the proper inductive relation to each other, but I prefer the form shown in Figs. 3 and l, in which the wires are braided together.

By the means described, I am enabled to tune a plurality of grid circuits simultaneously to the identical resonance period by a single tuning device. This results in a highly improved quality of tone, much greater selectivity and results as to signal strength and clarity obtained with a smaller number of amplification stages which compare favorably with results obtained with sets having a greater number of stages. I find it no longer necessary to provide elaborate devices for shielding the several radio frequency transformers from each other, because I rely upon the inductive coupling of these radio frequency transformers to accomplish my results. This simplifies the set very much, and makes it much cheaper to build and more etficient in action. Since no shielding is resorted to, I am'enabled to operate this radio receiving system with considerably less power than that required for other systems getting corresponding results. For instance, I am able to operate my system using a plate battery voltage of only 4.5 volts, as against the 90 volts commonly employed with similar systems. Because of the fact that I operate at lower plate voltage, I not only am able to operate the set more efficiently but I also secure better tone quality and have less static and similar disturbances because of the lower plate voltage employed. This ondary windings in the system results in a considerable economy in the manufacture of sets, since improved results can be secured with a fewer number of audions and other parts, and the parts e1nployed are less expensive and less diiilcult to make. It is not necessary to provide special- 1y balanced tuning devices, or variable condensers. It will be observed that the coil structure which I have provided, in which the several circuits are coupled with an identical inductive coupling, presents relatively high capacitive relationshipbetween the inductances, and this is directly contrary to the trend of more recent developments in this art, in which the efi'orts have been to make the radio frequency coils of as low capacity as possible.

I am aware that the system disclosed and described in this application may be changed considerably without departing from the spirit of my invention, and, claimed my invention broadly, as indicated by the appended claims.

What I claim is: V

1. In a radio receiving system, the combination of a plurality of cascaded audions, a plurality of radio frequency transformers, the secondaries of which are connected to the grids of said audions, a tuning circuit comprising a single tuning coil and a variable condenser, said secondaries and tuning coil being inductively coupled.

2. In a radio receiving system, the combination of a plurality of audions, a plurality of grid circuits connected to the grids of said audions, and a tuning circuit including a tuning device, wires forming parts of said grid and tuning circuits being braided together and the braid formed into a coil whereby identical inductive couplings are effected between said tuning and grid circuits.

3. In a radio receiving system, thecombination of a plurality of audions, a plurality of grid circuits connected to the gridsof said audions, a tuning circuit including a tuning device therein, wires forming parts of said grid and tuning circuits being symmetrically braided togetherand the-braid formed into a coil whereby said tuning circuit is inductively coupled identically with said grid circuits.

4. In a radio receiving system, the combination of a plurality of audions, a plurality of radio frequency transformers having secgrid circuits connected to the grids of said audions, and a tuning circuit, wires forming parts of said grid and tuning circuits being braided together and the braid formed into a coil, and the primary windings of said transformers bein inductively coupled with said coil,

5 In a radio receiving system, the combina ion of a pair of audions, a pair of radio frequency transformers, the secondary windtherefore, I have ings of which are connected to the grids of said tubes, a tuning circuit, said secondary windings and a lead in said tuning circuit being symmetrically braided together and the braid formed into a coil, a primary winding connected in the antenna circuit and 

